Bis (azidophosphoranes)

ABSTRACT

TNE CLASS OF HIGH MOLECULAR WEIGHT PHOSPHOROUS AND NITROGEN-CONTAINING COMPOUNDS HAVING TWO OR MORE PHOSPHORANE LINKAGES PER MOLECULE. THESE COMPOUNDS ARE INTERMEDIATES TO FIRE-REATRDANT POLYMER PHOSPHORANES.

United States Patent 3,629,296 BIS(AZIDOPHOSPHORANES) Roger A. Baldwin,La Mirada, and Ming T. Cheng, Buena Park, Califl, assignors to KerrMcGee Chemical Corp. No Drawing. Original application Nov. 15, 1965,Ser. No. 507,699. Divided and this application Nov. 12, 1968,

Ser. No. 793,630

Int. Cl. C07c 117/00; C09d /18 U5. Cl. 260-349 Claims ABSTRACT OF THEDISCLOSURE New class of high molecular weight phosphorus andnitrogen-containing compounds having two or more phosphorane linkagesper molecule. These compounds are intermediates to fire-retardantpolymer phosphoranes.

This is a division of application Ser. No. 507,699 filed Novv 15. 1965and now abandoned.

This invention relates in general to novel high molecular weightcompounds having two or more phosphorane linkages per molecule and totheir methods of preparation. More particularly, this invention relatesto the preparation or bis(azidophosphoranes), bis(halophosphoranes) andsuccessively higher molecular weight polyphosphorane condensationproducts and to novel processes for preparing such materials.

customarily, monomeric and polymeric phosphoranes have been prepared bythe direct reaction of a phosphonylazide with a tertiary phosphine toyield higher molecular weight phosphorane materials. When phosphonyldiazides are reacted directly with phosphines valuable polyphosphoranesare obtained which have utility as fire-retardants and thermally stableplastics. However, such a process, while feasible, is not completelypracticable commercially due to the serious safety problems arising byreason of the extreme shock sensitivity of organic phosphonyl diazidecompounds. Because of this instability of the diazides, commercialpurification of suitable monomers for polyphosphorane production has notbeen possible on a large scale. When impure phosphonyl diazides areutilized as starting materials without purification, the direct reactionwith tertiary phosphines under prior art methods gives polymericproducts with unsatisfactory physical and mechanical properties due toshort chain length. Thus it has long been desired to prepare thermallystable polyphosphoranes by way of stable easily purified bisphosphoranessuitable for larger scale industrial handling.

It is therefore an object of the present invention to provide a newclass of high molecular weight phosphorus and nitrogen-containingcompounds having two phosphorane linkages per molecule, suitable forpolyphosphorane production and to provide methods for the preparation ofsuch bis-substituted phosphoranes. Being stable such compounds arereadily purified for subsequent use in chemical polymerization andpolycondensation reactions.

It is a further object of this invention to provide a new and novelclass of mixed polyphosphoranes and new polycondensation productstherefrom, and suitable methods for preparing such compounds.

Additional objects and advantages of this invention not specifically setforth above, will become apparent during the course of the discussionwhich follows.

A new stepwise method of preparation of polyphosphoranes has beendiscovered which gives essentially quantitative yields of a new type ofproduct readily purified and suitable for further condensation to higherpolymers. This new method avoids the problem of isolating the highlydangerous phosphonyl diazides, and instead utilizes new 3,629,296Patented Dec. 21, 1971 ice and useful derivatives having excellentthermal and shock stability.

For a more complete understanding of the nature of this invention thefollowing chemical equations are presented, followed by illustrativeexamples. The basic chemistry involved in this new stepwise method maybest be understood in terms of its application to the preparation ofsimple azidophosphorane and azidothiophosphorane compounds, assummarized in Examples 1 to 3 below. These polymer prototype compoundshave excellent thermal and hydrolytic stability, and by furtherapplication of these methods to compounds having two phosphine groupsper molecule, the bisphosphorancs of the present invention have beenprepared.

The reaction of triphenylphosphine with phenylphosphenyl diazide wasfound to proceed in a stepwise manner under controlled conditions toform the azidophosphorane.

e s I( )(Na) a da Cu s )N= t s)a Na EXAMPLE I One mole of purifiedtriphenylphosphine recrystallized from isopropyl alcohol was dissolvedin pyridine and added to a crude solution of one mole phenylphosphonyldiazide freshly prepared from phenylphosphonyl dichloride. An exothermicreaction resulted, with evolution of one mole of nitrogen. The solutionwas concentrated at reduced pressure, and the residue recrystallized. Astable light colored solid was obtained with a melting point of to 126degrees C. Further purification and analysis showed the product to bephenylazidophosphonimidotriphenylphosphorane, C H N OP a whitecrystalline solid, M.P. l43-l45 C. Upon analysis the compound was foundto contain 14.1% phosphorus and had a molecular Weight of 438.

Attempts were then made to hydrolyze this compound by adding water to apyridine solution. Initially, the mixture became cloudy and after 30minutes additional water was added causing a white solid to precipitate.After stirring another hour, the mixture was filtered to yield, aftervacuum drying, a white powder, M.P. 148150 C. The infrared spectrum ofthis material was identical with that of previously obtainedazidophosphorane, having a strong azide absorption at 2138 cm.'-

An additional quantity of the azidophosphorane, about 2.1 g. (0.005mole) was stirred overnight with aqueous sodium hydroxide. Since thesample had not dissolved in this time, it was heated on a steam bath for8 hours without solution taking place. The sample was filtered, washedwith water, and vacuum dried to yield 2.1 g. (100% recovery) ofazido-phosphorane melting at 145 C. The slightly low and wide meltingpoint indicates some minor impurity although the infrared spectrum wasunchanged. Thus, the stable azidophosphorane could not be hydrolyzed tothe corresponding phosphonic acid.

In a similar manner it was found possible to synthesize anazidothiophosphorane by reaction of phenylthiophosphonyl diazide andtriphenyl phosphine.

Here also it has been found that a stepwise reaction ofthiophosphonyldiazide with tertiary phosphine yields products having newand unexpected advantages analgous to results obtained with thephosphonyl derivatives above.

EXAMPLE II One mole of purified triphenyl phosphine was dissolved inpyridine. A crude solution of freshly prepared phenylthiophosphonyldiazide in pyridine was slowly added under reflux conditions. Anexothermic reaction resulted and nitrogen was evolved. The product wasan oil with a characteristic infrared azide absorption at 2141 cm. andwas stable to hydrolysis. The product also showed a strong phosphorus tonitrogen double bond absorption at 1242 to 1220 cm. typical ofphenylazidothiophosphonimidotriphenylphosphorane. For furtheridentification the product was reacted with methanol. A solution of 0.02mole of starting material was used. It was necessaary to reflux thereaction mixture for about 36 hours in order to complete the reaction(as followed by infrared spectroscopy). After removal of the solvent atreduced pressure and digestion with methanol, 4.5 grams (0.01 mole, 50%yield) of the desired methoxythiophosphorane was recovered.Recrystallization from methanol and Norite A gave an analytical samplemelting at 121- 123 C. Further purification and analysis showed theproduct to be C H NOP S with 3.17% nitrogen, 14.1% phosphorus and 7.02%sulfur.

Under the new controlled stepwise methods of reaction of the presentinvention for converting phosphines to phosphoranes, the synthesis ofmonohalophosphoranes proceeds as follows:

The resulting chlorophosphorane is a relatively reactive compound,forming the corresponding acid, on hydrolysis, in quantitative yield.

Subsequent reaction of such mono-halo compounds with sodium azideprovides an alternate source of azidophosphoranes without the necessityof handling the potentially hazardous phosphonyldiazides, which theprior art teaches are necessary starting materials.

The synthesis of a typical haloazidophosphorane was carried out in thefollowing manner.

EXAMPLE III One mole of phenylphosphonyl dichloride and one mole ofsodium azide in pyridine solution were stirred at 20 C. for 18 hours.One mole of triphenylphosphine in pyridine was then added. The mixturewas cooled in an icewater bath during the addition. The exothermicreaction yielded one mole of nitrogen. The mixture was warmed andrefluxed for one hour. The product was found on analysis to bephenylchlorophosphonimidotriphenylphosphorane. The yield was 98%.

When a portion of the above solid was mixed with water, first an oil andthen a solid was formed. Recrystallization from methanol and water gavea white crystalline precipitate, with a melting point of 205-206 C.Analysis proved the compound to be C H NO P with 14.6% phosphorus and aneutral equivalent of 413.

Another portion of the above solid was dissolved in pyridine and treatedwith an equimolar quantity of sodium azide over a period of 6 /2 hours,and the reaction mixture poured into water, a white precipitate ofphenylazidophosphonimidotriphenyl phosphorane was obtained. The yieldwas 97% of this compound melting at 142- 145 C.

Thus, it was found that under certain conditions a phenylphosphonyldiazide and triphenylphosphine react in a very clearly defined stepwisemanner to yield an azidophosphorane which is thermally stable andresists hydrolysis. The product may be safely stored or purified forfurther reaction to the phenyldiphosphorane. When this method wasextended to certain difunctional phosphines it was found thatquantitative yields of new high molecular weight bisphosphoranes result,the products having pendant azido groups at each end of the molecule.

A typical compound of the present invention, also known as abis(azidophosphorane), may be prepared by direct reaction of crudephenylphosphonyl diazide and a bis(tertiary phosphine). The productexhibits extreme thermal and hydrolytic stability and is readily solublein the usual organic solvents making it relatively simple to purify suchproduct or to carry out further polycondensation reactions. Thepreparation of N,N'-[p-phenylenebis (diphenylphosphoranylidyne)]bis(Pazido P phenyl phosphonic amide) may be represented as follows:

A solution of one mole of phenylphosphonyl dichloride was treated withtwo moles of sodium azide in pyridine, and allowed to stand for 18hours. A pink solution resulted. To this was added a slurry of one moleof 1,4 bis (diphenylphosphino) benzene and 50 ml. of pyridine. Theinitial reaction rate was rapid and exothermic and essentially completein 0.5 hr. The nitrogen collected was found to be essentiallyquantitative. Salts were removed by filtration through a sintered glassfunnel. Removal of the solvent at reduced pressure provided a tackyresidue from which a quantity of the bis(azidophosphorane), M.P. 136l38C. was isolated. The product was found to have a molecular weight of820, compared to 806 theory by the Neumeyer method.

The infrared spectrum of this material showed a strong azide at 4.72microns as well as the typical phosphorane spectrum from 7-9 microns. Inaddition, there was a marked absence of any absorption at 10.4-10.9microns which might have been ascribed to absorption as a result ofhydrolysis. The infrared spectrum thus resembled the spectrum of purecompound prepared in pyridine. Analysis provided the compound to be C HO N P with 15.5% phosphorus.

EXAMPLE V The phenylphosphonyl diazide (2 moles) (Example IV) wasprepared in a benzene pyridine solvent system with a molar ratio of 2:1for the pyridine and phenylphosphonyl dichloride and then reacted withone mole of 4,4-bis- (diphenylphosphino)biphenyl in benzene at roomtemperature. For about one and one-half hours a stream of nitrogen wasevolved. The mixture was filtered and the solvent removed from thefiltrate to yield pale yellow solid with a melting range of ISO-200 C.The yield of this crude product was quantitative. The latter was thenwashed several times with acetone to yield a white solid with a meltingpoint of 210-2l2 C. The infrared spectrum was similar to that of theproduct made in Example IV including a strong azide absorption in theregion of 4.70 microns. Analysis proved the compound to be with 14.1%phosphorus. The overall yield was 75% of the biphenylbis(azidophosphorane) also known as N,N'-[pbiphenylenebis(diphenylphosphoranylidyne)] bis (P- azido-P-phenylphosphonic amide).

The present invention further includes a process for the preparation ofa second new and previously unknown class of compounds, thebis(halophosphoranes). Such compounds are obtained by a similar stepwisereaction of phosphonyldihalide with one equivalent of sodium azide toyield a monohalophosphonyl azide and subsequent reaction of the productwith a compound having two pendant tertiary phosphine groups permolecule.

The resulting bis(halophosphoranes) may then be further converted intobis-azido compounds by the method of Example IV utilizing two moles ofsodium azide per mole of bis(halophosphorane). Suchbis(halophosphoranes) also were found to have chemically active halogengroups which readily undergo condensation reactions with polyamines andpolyglycols to produce phosphorane-bearing polyesters and polyamides ofa new and novel nature.

EXAMPLE VI One mole of phenylphosphonyl dichloride was reacted with 1.0mole of sodium azide dissolved in dry pyridine by stirring at roomtemperature for 18 hours. Thereafter 0.5 mole ofl,4-bis(diphenylphosphino) benzene in pyridine was added, cooling themixture in an ice-bath during the addition. The product was obtained byremoval of the solvent and crystallizing. Analysis and infrared spectrashowed the product to be the bis(chlorophosphorane), also known asN,N'[p-phenylenebis-(diphenylphosphoranylidyne ]-bisP-chloro-P-phenylphosphonic amide).

This product was then dissolved in a mixture of benzene and pyridine andstirred with two moles of sodium azide. The rapid foregoing reaction wascomplete in six hours. The salts were filtered under nitrogen pressure;and the filtrate concentrated to yield a tan powder. The product wasfound to be identical to the bis(azidophosphorane) of Example IV.

EXAMPLE VII One mole of the bis(chlorophosphorane), prepared as inExample VI, is dissolved in dimethylformamide. One mole of hydroquinoneis slowly added until the evolution of HCl ceases. The mixture is heatedwith a stirring until a thick mass of polymer is obtained. The resultingphosphorane-containing polyester can be vacuum distilled to removediethylformamide solvent and other volatile materials and yield a linearpolymer:

CIBHE Ce s O-CBH4OP(0)N=P-CflH4P=NP(O)- (MR5 CsHs CoHs CtH x where xindicates the degree of polymerization.

EMMPLE VIII One mole of bis(chlorophosphorane), prepared as in ExampleVI is dissolved in dimethylsulfoxide. One mole of p-phenylenediamine andtwo moles of triethylamine are added. Heating at reflux temperature andremoval of the salts and volatiles in vacuo yields a linear polymer:

where x is the degree of polymerization.

The polyesters and polyamides of Examples VII and VIII thus modifiedwith phosphorane linkages possess unique properties as fire retardantmaterials and as modifiers of conventional polyamides and polyesters.

The bis-halo and bis(azidophosphorane) compounds of Examples IV, V andVI are readily soluble in organic polymer solvents such as pyridine,dimethylformamide and dimethylsulfoxide. Solutions of these purecompounds can then be subjected to further high temperature condensationreactions under optimum controlled conditions not possible in previouslyknown systems which required that the hazardous crude phosphonyl diazidereaction mixtures remain in low boiling point solvents for subsequentpolymerization reactions.

The product of Examples IV and V, the bis(azidophosphorane), can beconverted to a tetraphosphorane by reaction with triphylphosphine inbenzene, toluene, or similar hydrocarbons. When the reaction is carriedout in pyridine, dimethylformamide or dimethylsulfoxide excellent yieldsof tetraphosphorane are obtained.

EXAMPLE IX One mole of triphenylphosphine was dissolved in pyridine and0.5 mole of the bis(azidophosphorane) (Example IV) was added at refluxtemperature. The nitrogen evolved was 96% of the theoretical amount.Removal of the solvent under reduced pressure and recrystallizationyielded 91% of light yellow crystals melting at l01103 C. Analysisproved the compound to be the tetraphosphorane, C78H54O2N4P6 with 14.3%phosphorus and a molecular weight of 1250 compared to the theoreticalvalue of 1275.

Subsequent reaction of the bis(azidophosphorane) of Examples IV and Vwith 1,4-bis(diphenylphosphine) benzene in a variety of solvents such asdimethylformamide, dimethylsulfoxide or hexamethyl phosphoric triamideresulted in unique polyphosphoranes from which numerous fibers and diskswere formed. The products of such controlled polycondensation representa useful class of polyphosphoranes possessing unusual properties. Morethermally stable phosphorane resins are obtained by a careful control ofthe purity of the reacting monomers, and of the stoichiometry of thereacting components. In addition these high temperature stable resinsare more resistant to hydrolyzed phosphonyldiazide compounds in thepolymers. Moreover, the use of more elfective polymer solvents makes itpossible to monitor the polymerization reactions through the use ofstandard instrumental control methods until products of specifiedmolecular weights are obtained.

Depending on the choice of reactants these polymeric phosphoranes areuseful as ablative materials and as structural plastics. High molecularweight polymeric phosphoranes provide new thermally stable polymerswhich can be drawn into fibers, fabricated into flm and sheet laminates,or incorporated into varnishes for use as surface coatings. Thephosphorus content of these products imparts a high degree of resistanceto combustion, giving them an additional utility as fire-retardantmaterials, and as polymer modifiers.

While the process of preparation of the bis(halophosphoranes) andbis(azidophosphoranes) of the present invention is conveniently carriedout at room temperature initially, followed by periods of heating at thereflux temperature of the pyridine solvent to C.) the reactiontemperatures can range from 20 C. to C. depending upon the choice ofsolvent and chemical and physical properties of the reactants. Thecompounds of the present invention can be prepared in a variety ofsolvents such as pyridine, acetonitrile, triethylamine, di n-butylether, benzene, toluene, dimethylformamide, dimethylsulfoxide and thelike. Depending upon the partic ular halogen substituent used, such asfluoride, chloride, bromide and iodide and the number and type ofsubstituents on the phosphorus compounds the reaction time may also varyfrom a few hours to a few days.

It should be noted that the bis(azidophosphorane) of Examples IV and VImay be separately isolated and thereafter reacted with a differentbistertiary phosphine than that used for the preparation of thebis-azidophosphoranes. By this technique for the first time it hasbecome possible to vary the properties of the final polyphosphoranes.

This is one additional manner in which the stable bis (azidophosphorane)materials of the present invention have a unique utility and lead topolyphosphorane materials of superior properties.

While the present invention has been described in terms of what atpresent are preferred embodiments thereof, it will be understood, ofcourse. that various changes. substitutions, modifications and the likemay be made therein Without departing from the true scope of theinvention as defined in the appended claims.

What is claimed is:

1. A composition of matter consisting essentially of abis(organophosphorane) derivative selected from the class consisting ofwhere R is selected from the group consisting of phenyl and methylgroups.

2. A composition of matter having the formula:

where R is selected from the group consisting of phenyl and methylgroups;

Y is selected from the group consisting of phenylene,

biphenylene and diphenylene ether groups; and

Z is selected from the grip consisting of oxygen and sulfur. 3.

C0115 CG fI c6115-P(O -N=i -C,H4P=NP(O)CHi sta cunt C6116 N3 cuts (30115cflu5-Pt0)-N=P-cuic@mP=NP(0)-o6H5 N; leHs (30115 I l;

@611 CIUIIB C5II5-P (O)N=PCeHi-OC H4P=N-P(O)C H5 N; can (16115 N;

CHs (7H3 cant-1f 0 -N=P-oHtP=N-P(0)otH5 References Cited UNITED STATESPATENTS 3,317,595 5/1967 Paciorek 260-551 OTHER REFERENCES 0 Baldwin,A.C.S. Abstracts of Papers, 146th meeting HENRY R. JILES, PrimaryExaminer C. M. SHURKO, Assistant Examiner US. Cl. X.R.

UNITE sures PATENT swish CEWMAE QCREQ'HCN Patent NO- 52 9: DatedDecember 3 Inventor(s) Roger A, Baldwin and Ming T.a Cheng It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 2, line 16, "phenyl should read phonyl lines 19-21 the equationshould read: aHsr wmsi 6H5)8P 2: GHB1 )N=P( SHS)3 N2 Column line 45,rovided should read proved Column 5, lines 51-5 the formula should read:CGHS e 's -O-C6H4-O-P(O)--N=P--C6H4-P=N P(O)- I i i I 0 21 0 1-1 CSHSColumn 6, line 48, "flm" should read film Column 7, lines 29-53, theformula should read:

Column 8, lines 15-19, the formula should read:

C H C6H5 C6H5-P(O)-N=P-C6H4-O-C6H4-P=N P(O)-C6H5 I I 8 i N3 c n S S HeSigned and sealed this 30th day of May 1972.,

(SEAL) Attest:

EDWARD MELETCHER, JRo ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents F ORM PC4050 (10-69) USCOMM-DC 60376-P69 fi' U.S. GOVERNMENYPRINTING OFFICE: 1969 0366-3S4 UNITED STATES PATENT orrihr CER'HWQAEE Ci@CRRECHCN Patent No. 9, 9 Dated December 1971 Inventor(s) Roger A,Baldwin and Ming To Cheng It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 2, line 16, "phenyl" should read phonyl 0 lines 19-21$ theequation should read:

e s e e 5)e 2 6H51 )N=P(%HS)3 +N2 Column line 45, rovided should read weproved Column 5, lines 51-5 the formula should read:

C H C l-I Column 6, line 48, "flm" should read film Column 7, lines29-55, the formula should read:

Column 8, lines 15-19, the formula should read:

C6H5 0 x1 N3 C H5 S S 8 Signed and sealed this 30th day of May 1972.,

(SEAL) Attest:

EDWARD M,FLETCHER, JR.a ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents F ORM PO-1050 (10-69) USCOMM-DC 60376-P69 U.5. GOVERNMENTPRIN ING OFFICE: 1989 0-365-336

